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STTEDIT-4 Show backend error details in the template preview - #121
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The preview discarded the error object from the preview request, so a failed render only produced a generic message. mod-template-engine returns a diagnostic and, depending on the resolver, a source line with a caret; that detail is now extracted in the query function and shown below the generic message. Extraction happens in the queryFn because reading the response body is async while react-query exposes `error` synchronously.
thomas-sc
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August 19, 2026 09:00
zburke
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Aug 19, 2026
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Your detailed explanation of both the implementation and why we need it was super helpful; thank you!
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Thanks @zburke , glad it was helpful. Is anything else needed to merge? |
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A failed backend-rendered preview only showed the generic "The preview could not be rendered."
useTemplatePreviewdropped the error object, so the diagnostic thatmod-template-enginereturns was lost. A syntax error in a large template is currently a needle in a haystack.queryFn(reading the response body is async whileerroris exposed synchronously) and attached to the thrown error.BackendPreviewrenders the diagnostic below the existing generic message, plus a short excerpt of the source line with a caret where the response carries one; the full template dump is not rendered.errors[].message); with no extractable detail the generic message is shown on its own.How much detail arrives depends on the resolver: mustache.java returns one line without a position, the Handlebars resolver from MODTEMPENG-136 adds a source line and a caret. The parser does not assume the richer shape, so MODTEMPENG-136 is not a prerequisite. Both real responses are used as test fixtures.
Backwards compatible: no new or changed props, no dependency changes. Only the existing error state gains detail, and it is reachable solely for consumers that already opted into
previewRenderer="backend". ui-circulation and staff slips keep the regex preview. No new interactive UI, so accessibility is unchanged.mustache.java — diagnostic line only, no excerpt:
Handlebars (MODTEMPENG-136) — diagnostic, excerpt and caret:
Refs STTEDIT-4